Dirac >> Feynman?

Information Processing points to a review by Freeman Dyson in the New York Review of Books of Perfectly Reasonable Deviations From The Beaten Track: The Letters Of Richard P. Feynman .

What I find interesting in the article is Dyson’s claim that Paul Dirac was a greater genius than Richard Feynman. Of course, judging “greater genius” seems about as silly as worrying about whether it is a “double backward doggy dare” or a “triple backwards over-the-top doggy dare.” With this caviot, I however, just have to say “huh?”

In my mind Dirac has three claims to genius: his derivation of the Dirac equation, his work on magnetic monopoles (showing that the existence of a single such monopole could explain the reason charge comes in discrete quantities), and his work unifying the early differing approaches to quantum theory. Feynman, in my mind, has four or more claims to genius: his derivation of the path integral formulation of quantum theory, his space-time approach to solving the problems in quantum electrodynamics, his work on the theory of superconductivity (showing the importance of quantum theory on a “macroscopic” level), and his model of weak decay (work with Gell-Mann which was also independently done by George Sudharsan and Robert Marshak.) So in my mind, I put Feynman just above Dirac (what, you mean you don’t have your own personal ordering of geniuses?)

And, after thinking about it for a while (too much time, perhaps!) I think I can guess why Dyson puts Dirac above Feynman (oh, to be a physicist known by your last name alone!) I believe the reason is that Dyson was originally a mathematician. Feynman’s work is filled with the sort of raw physical insight that physicists love and admire. Sure, making the path integral rigorous is a pain the rear, but it works! In Dirac’s work, we find, on the other hand, a clear mathematical beauty: the Dirac equation and the magnetic monopole are motivated more my arguments of symmetry than by any appeal to a physicist’s “calculate and run” methodologies (indeed the latter is not even known the correspond to experimental reality!)

So who is the greater genius? Well I “double dog dare you” to come up with reasons that Dirac is a greater genius than Feynman.

Update: See the comments for some fun back and forth. OK, in my head really I put Dirac and Feynman at the same level. What I find intersting is how one’s background influences this (silly) debate. If you are a particle theorist, I bet Dirac>Feynman. If you went to Caltech as an undergrad, I bet you have Feynman>Dirac. Ah, the ways theorists waste away their days.

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34 Responses to Dirac >> Feynman?

  1. Wolfgang says:

    But Dyson thinks that one of Feynman’s achievments was already in one of Dirac’s papers.
    Thus its 4:3 for Dirac …

  2. Wolfgang says:

    Dave,

    according to Dyson:
    Feynman always said, whenever the opportunity arose, that the “space-time approach” that led him to his new way of doing particle physics was directly borrowed from a paper of Dirac’s.

    So, R.P.F. himself suggests it was 4:3.
    But then Dirac knew nothing about Tanu Tuva.

  3. Wolfgang says:

    Dave,

    you forgot the 1+3 gravity formalism (separating dynamics and constraints) on Dirac’s side and
    thus it would be something like 4 vs 4-

  4. Wolfgang says:

    While there is a Dirac medal, there is no Feynman medal. So Dirac has to be more important …

  5. Wolfgang says:

    and how could I forget Dirac’s large number hypothesis, which continues to inspire crackpots …

  6. Wolfgang says:

    > Guess Einstein scores pretty high on this scale.

    Of course Einstein is a special case because:
    i) he was bad at school
    ii) he was bad at math
    iii) he worked outside the establishment (at the patent office)
    iv) later in his career. he acknowledged that relativity could not be correct

    Thus he continues to inspire people in similar situations.

    PS: for the “irony challenged” readers: I am kidding on all four points

  7. Dave Bacon says:

    Yeah, I totally disagree with Dyson’s thoughts ont his matter. It’s hard to tell if Dyson is refering to path-integral or whether he is refering to work on QED. Certainly in the former, it is true that Dirac wrote down an important starting idea. But it is also certainly true that Feynman ran with this idea and came up with the path integral, something which Dirac’s genius, I don’t believe, should be given credit for (in fact I would claim that this is a sign of the greater brilliance of Feynman over Dirac: Feynman saw that you could string together infinitesimal evolutions and you obtained this beautiful exp(i Action) term.

    On the other hand, Dyson says “space-time approach” which may refer to Feynmans work on QED. Here, I can’t make heads or tails of why Dyson would claim that Feynman’s work was really Diracs. Certainly there are ideas in this work which are fundamentally Dirac’s: Feynman is, after all, using propogators for the Dirac equation. But the important insights in that paper, how to use these tools to carry out renormalization, etc. I don’t think Dirac should get credit for this.

    So I say 4:3 for Feynman. Plus I’d also give one more to Feynman for quantum computers, but I figure I’m pushing my luck with that one 😉

  8. Frank says:

    I think the concept of the delta Dirac function, also very fishy from the mathematical point of view at the time of introduction, has lead to much more farreaching insights in all sorts of branches of science than the path integrals.
    Besides, I think Dirac was the first to formalize Quantum Mechanics by talking about operators in a Hilbert space (which at the same time includes Heisenberg’s and Schrodinger’s versions), and as such was one of the founding fathers of QM.
    I would certainly vote for Dirac

  9. Dave Bacon says:

    Perhaps our opinions will split along our different nationalities?!

  10. Dave Bacon says:

    Wolfgang,

    Which is puzzling!

    Why? Because, like I said, if he is talking about the path integral, then sure, Dirac wrote down the infinitesimal propogator and said it was “analogous” to exp (i Lagrangian). But certainly this is only a small step in conceiving the path integral approach no? (bad pun, sorry.) If you look at Feynman’s Nobel lecture, and read Diracs paper, it seems to me that there is no doubt that Feynman may say something like “yeah it was all founded upon this one equation in Dirac’s paper” but this is just modesty (and Feynman loved Dirac, btw!) There is also a comment somewhere, I don’t recall where, that Feynman actually explicitly asked Dirac whether he knew that “analogous” actually meant “equal” and Dirac said “no.”

    So I’m not sure why Dyson made this comment. He certain is in a better position than any of us to know this, but it seems to contradict the history I’ve learned.

    • Mike Porter says:

      If memory serves, I believe Dirac replied “Is it?” And then walked off as if to leave the question dangling….

      but what do I know….

  11. Dave Bacon says:

    No, we can’t have a tie!

    How about Feynman’s derivation of gravity as a spin 2 field?

    Since Dirac gets the magnetic monopole, which we haven’t ever observed, should we give Feynman the Parton model. Not quite right, but surely very influential and interesting?

  12. Dave Bacon says:

    Also note there is a famous quote on this matter. Wigner said “He is a second Dirac. Only this time human.” So I guess we can say that Wigner votes there genius equal? LOL.

  13. Dave Bacon says:

    I like it, a new definition of genius: “The number of crackpots you inspire.” Guess Einstein scores pretty high on this scale.

    And remember, they gave a Dirac prize to someone who does quantum computing…so how prestigious could it be (to be clear peoples, this is sarcasm.)

  14. Paul says:

    Why didn’t you count antimatter amongst Dirac’s acheivements?

    Not being willing to accept the parton model on Feynman’s side I think that’s 5-4 to Dirac.

  15. Dave Bacon says:

    I did count anitmater: the Dirac equation. This was, I think, Dirac’s greatest achievement, and it predicted antimater. But even Dirac had a hard time believing this result, and attenpted to think about the electron’s partner as the proton. Didn’t work, for reasons which Pauli quickly pointed out (Pauli must surely be physics greatest critic.)

  16. Sepiraph says:

    I think Feynman himself would say Dirac since Dirac is Feynman’s hero.

  17. sein htoon says:

    Feynman was a genius of the calibre of Tomonaga,Schwinger and Dyson. And using a classification due to a renown Russian physicist Landau who many said was the the Russian answer to Feynman-they would be placed in the First Class. But Dirac would belong to a different league which would certaintly include Einstein and Newton – a Half Class! It appears that
    Einstein always carried around a copy of Dirac’s text on quantum mechanics, and he spoke admiringly of “Dirac to whom in my opinion we owe the most logically perfect presentation of quantum mechanics”. (See N Mukunda’s article in Resonance August 2002)

  18. david says:

    The qoute by Newton, “If I have seen further it is by standing on ye shoulders of Giants” applies to most great scientists. Dirac was one of the few who were just giants.

  19. nigel cook says:

    Dirac did write a crucial paper about the path integral in 1933, called “The Lagrangian in Quantum Mechanics”.

    That Dirac paper is reprinted (together with Feynman’s PhD thesis, “The Principle of Least Action in Quantum Mechanics”)) in the book “Feynman’s Thesis: A New Approach to Quantum Theory” (laurie M. Brown, editor, World Scientific Publishing, London, 2005). The introduction to that book is available online: http://www.worldscibooks.com/phy_etextbook/5852/5852_preface.pdf

  20. Dave Bacon says:

    The interesting thing about that paper, of course, was the Dirac did not interpret his results in the way that Feynman did. Dirac wrote the equations, Feynman interpreted the poetry 🙂

  21. Oscar says:

    I’ve read almost every Feynman book available. Obviously, you are biased toward Feynman, and for good reason, he was a physicist of the highest order. I believe another reason people love him was due to his funny and charismatic character, and the fact that he was a great teacher. Dirac was the contrary in these regards, he was a recluse, dry, and highly antisocial. These traits guaranteed that Dirac was never in the public eye, Feynman, like Einstein reveled in stardom and fame.

    I’m currently reading The Strangest Man, a biography of Paul Dirac, and as much as I admire and like Feynman, Dirac owns him. Dirac worked alone, whereas
    others like Heisenberg, had Pauli, Jordan, Born to help him. Paul’s version of quantum mechanics developed by himself at the age of 28, was according to Einstein, the most clear and elegant presentation of quantum mechanics. Einstein even carried Dirac’s book, The Principles of Quantum Mechanics, wherever he traveled. The only thing that bugged Einstein about Dirac was his strangeness, he once said it was awful to border between genius and madness like Dirac tried to balance.

    Dirac was a father of quantum mechanics, Feynman built on Dirac’s work. It is doubtful that Feynman could have just invented it, smart as he was. Lev Landau, the famous physicist who won the Nobel for Superfluidity of helium, used to rank physicists on a log scale. The highest was Einstein at .5, Dirac, Heisenberg, and Schrodinger he gave a 1. Landau ranked himself a 2.5 and later a 2.0…

    I personally think Feynman was a 2.0 or a 1.5… A bit lower than Dirac.

    Dirac was not a physicist, he was a magician. Anyway, that’s my 2 cents.

    • Schwinger says:

      I’d rank Feynman a .5 as well but, hey, what do I know.

      I’d also give Max Born a .5 as well, and Leo Szilard should’ve definitely received a Nobel Prize (one of histories great screw-ups).

      Dirac was phenomenal though. I’d rank him top 7 physicists of all-time only behind Einstein, Newton, and Maxwell.

  22. Mike Porter says:

    I suppose one could ask, “who is better, da Vinci or Michelangelo?” My belief is that there is no answer as they were creative in different ways but none the less, creative.

  23. eli says:

    Feynman was a clown who got into the circle these top scientists and played along. The path integrals are due to Dirac: dirac had a paper, known as Dirac’s little paper, in which he used path integral approach to QM. He just hated them since they did not make sense mathematically (convergence etc). They were also used by Norbert Wiener. Feynman extended the “little paper” and earned a Nobel Prize. Feyman Diagrams were just illustrations/simplification and not much noteworthy. He was the first science James Bond and did manage to live fully too.

    Dirac is O(Einstein). He was real deal.

    • Schwinger says:

      There was difficulty reconciling the Newtonian theory of gravitation with its instantaneous propagation of forces with the requirements of special relativity; and Einstein working on this difficulty was led to a generalization of his relativity—which was probably the greatest scientific discovery that was ever made.

      P. A. M. Dirac, quoted in Chandrasekhar, S. “On the “Derivation” of Einstein’s Field Equations.” American Journal of Physics 40.2 (1972): 224-234.

      I’d rank Einstein and Newton a 0, then Dirac and Maxwell a 0.5 but it’s like picking between a Lamborghini and a Ferrari, can’t really go wrong. Dirac was a phenomenal thinker. (You are supremely underrating Feynman though).

    • Edmundo says:

      I agree with you. I was exactly what I thought when I studied Dirac’s books and papers with those of Feynman, when I was student. When I compared Dirac’s work with Feynman’s work, I was very surprised that there was no mention at all on Dirac contribution to path integral in quantum mechanics. I remember I told my supervisor that Dirac had practically implemented the path integral approach of quantum mechanics and had given the correct connexion between classical action and transition probability associated with a path. My supervisor told me the difference was that that Dirac formulated it in terms of a proportionality and Feynman in terms an equality, and Feynman took advantage of it and continued. But for me, his answer did not change my mind of who really invented the concept of path integral and its connection with quantum mechanics.

    • Edmundo says:

      I agree with you. I was exactly what I thought when I studied Dirac’s books and papers and those of Feynman, when I was student. When I compared Dirac’s work with Feynman’s work, I was very surprised that there was no mention at all on Dirac contribution to path integral in quantum mechanics. I remember I told my supervisor that Dirac had practically implemented the path integral approach of quantum mechanics and had given the correct connexion between classical action and transition probability associated with a path. My supervisor told me the difference was that that Dirac formulated it in terms of a proportionality and Feynman in terms an equality, and Feynman took advantage of it and continued. But for me, his answer did not change my mind of who really invented the concept of path integral and its connection with quantum mechanics.

  24. Pakka says:

    Indeed, I think Feynman wouldn’t have shine so brightly if Dirac didn’t paved the way.

  25. Born Max Born says:

    Feynman was a genius, there is no doubt about it. Dirac did pave the way for him, but that’s like taking points away from Newton and Leibniz because Fermat and Descartes (and others) paved the way for differential and integral calculus.

    There are much closer than people think; I would give Dirac the slight edge but Feynman is a top 10 physicist of ALL-TIME.

    Honorable mention to: Julian Schwinger and Leo Szilard, two of the more underappreciated physicists of all-time.

  26. Mike Porter says:

    So who had the fastest mile time?

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